<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>02_JS的变量与常量</title>
</head>
<body>
<script>
  var a = 1;
  console.log(a);
  var b = 3.14;
  console.log(b);
  var c = 'hello world';
  console.log(c);
  var d = true;
  console.log(d);
  a = 5.5;
  console.log(a);
  var a = '哈哈哈我又来了';
  console.log(a);

  //ES6新增了let关键字声明变量
  let x = 1;
  console.log(x);
  x = 5.5;
  console.log(x);
  //重复声明
  // let x = 'let关键字声明的变量不能重复声明';
  // console.log(x);

  //使用const关键字声明常量
  const PI = 3.14;
  console.log(PI);
  //常量不能重复声明
  // const PI = 3.1415926;
</script>
</body>
</html>
